It is known in the art to use coated articles in the context of window units such as insulating glass (IG) window units. For example, see U.S. Pat. No. 6,632,491, the disclosure of which is hereby incorporated herein by reference. In the '491 patent for example, a solar management coating (e.g., low-E coating) is provided on the inner surface of one of the glass substrates of an IG window unit so as to protect a building interior against infrared (IR) radiation and the heat generated thereby. Coated glass substrates of IG units often have to be heat treated (e.g., tempered), prior to IG unit assembly, to meet certain code requirements.
FIG. 1 is a flowchart illustrating processing steps carried out during the conventional manufacture of an IG window unit. First, a glass substrate is coated with a low-E and/or solar control coating (step 1). An example low-E coating is typically a multi-layer coating which includes at least one IR reflecting layer of a material such as silver that is sandwiched between at least a pair of dielectric layers. The coating is typically applied via sputtering or the like. After the coating is applied to the glass substrate, the coated sheet is dusted with Lucor™ powder for purposes of protection (step 3). As is known in the art, the Lucor powder helps separate the coated sheets from one another during shipment to an IG unit fabricator, because during shipment a plurality of coated sheets are typically wrapped in a single rack. In particular, the powder is provided in order to reduce the likelihood of damage (scratching) occurring during shipment of the coated sheets.
Once the dusted coated sheets arrive at the IG unit fabricator, the fabricator typically stores the coated sheets in a rack or on a pallet (step 5). When the sheets are ready to be used, the coated sheets are each cut into smaller piece(s) (step 7) and edge seamed (step 9) as known in the art. Following cutting and edge seaming, the coated sheets are washed at a washing station using water and optionally soap of some sort (step 11). Following washing, a post-wash handling period typically occurs where the coated sheet is handled by operators or the like some of which tend to wear gloves (step 13).
Thereafter, the coated sheets are placed in a furnace and are thermally tempered therein (step 15). Thermal tempering at the fabricator typically involves heat treatment of a coated sheet using furnace temperature(s) of at least 580 degrees C., more preferably of at least about 600 degrees C. and still more preferably of at least 620 degrees C. An example heat treating furnace temperature is from 600 to 700 degrees C. This tempering and/or bending can take place for a period of at least 4 minutes, at least 5 minutes, or more in different situations.
Unfortunately, the process described above with regard to FIG. 1 is undesirable in that the coated glass sheets are often damaged during the process. Coated glass sheets are sometimes less durable while in the annealed state (i.e., prior to tempering). Thus, the glass sheets provided with low-E coatings thereon are highly susceptible to damage during each of steps 3, 5, 7, 9, 11 and 13 illustrated in FIG. 1. The coated side of the coated sheets are the most vulnerable to damage (e.g., scratching) in this regard.
For example, coated sheets are often scratched due to one or more of: (a) rubbing up against other sheets or the like during shipment; (b) pliers used by glass handlers during and/or proximate steps 7 and 9; (c) abrasion caused by gloves worn by glass handlers during any of steps 3, 5, 7, 9, 11 and 13; (d) brushes during washing step 11; and (e) other types of rubbing/abrasion caused during any of steps 3, 5, 7, 9, 11, and 13. Additionally, corrosion is also a significant cause of damage and is often caused by high humidity conditions, acid rain, and/or other materials which tend to collect on the coated articles during transport, storage and/or handling.
While the aforesaid types of damage often occur prior to heat treatment (e.g., tempering), the tempering of the coated sheets typically magnifies such damage. For example, a minor bit of corrosion which was caused pre-tempering can lead to a significant blemish upon heat treatment which causes the coated sheet to be scrapped. The same is true for scratch damage because scratches in a coating allow oxidation to occur deep within the coating and possibly at the silver layer(s) during heat treatment (e.g., tempering) since heat treatment is typically conducted in an oxygen-inclusive atmosphere. Thus, the damage to a coated article often tends to be worse following heat treatment. Accordingly, it can be seen that yields appreciably suffer due to pre-HT damage that tends to occur to coated glass sheets.
In view of the above, it can be seen that there exists a need in the art to better protect coated glass sheets in the processing stages prior to heat treatment (e.g., prior to tempering). In particular, increased protection against mechanical abrasion and environmental damage is needed. Over the years, numerous attempts have been made in this regard.
The dusting of coated sheets with Lucor powder separator is carried out in an attempt to better protect coated glass sheets in the processing stages prior to heat treatment. Unfortunately, Lucor powder provides no protection against corrosion damage, and also is not particularly effective in protecting against scratch damage related to the use of pliers, brushes, gloves and the like (e.g., see FIG. 6).
Encapsulating of racks during shipment has also been tried. However, encapsulating racks is labor intensive and has proven only partially effective during shipment. Moreover, it provides no practical protection during cutting, edge seaming, washing, and post-wash handling processing.
Special processing requirements are also undesirable since this severely limits the number of fabricators capable of performing such processing. Moreover, this significantly adds to the cost of fabrication and is highly undesirable in this regard.
Sacrificial lites (or glazings) have been used during shipment in an attempt to solve the aforesaid problems. In particular, glass sheets are run through the coater with the coater turned off and are subsequently loaded onto the shipping rack at an end thereof with the rack thereafter being wrapped for protection. Because the sacrificial lite is located at the end of the rack, some marginal protection to the other lites in the rack is afforded during shipment. The sacrificial lites are discarded at the fabricator. However, this technique is undesirable in that it requires coater downtime, wasting of glass, and wasting of shipping volume/space/weight, all of which lead to significantly cost increases.
U.S. Pat. No. 6,682,773 to Medwick discloses a technique where a water-soluble temporary protective layer is applied to a coated glass sheet via a liquid solution. In particular, the protective layer is an aqueous coating composition containing a polyvinyl alcohol polymer which may thereafter be removed by washing in water. Unfortunately, the technique of the '773 patent is highly undesirable in that: (a) the coating is applied in liquid form and thus requires a sophisticated heat drying process which takes up valuable time and space; and (b) the coating is typically water soluble and is removed by washing thereby leaving the coated sheet exposed to potential damage during post-wash handling and/or processing. Thus, it can be seen that the technique of the '773 patent is highly undesirable.
U.S. Pat. No. 6,461,731 discloses a protective diamond-like carbon (DLC) layer provided over a low-E coating. However, the DLC layer of the '731 patent cannot practically and reasonably be removed prior to tempering.
U.S. Pat. No. 4,710,426 discloses a protective polymeric layer on a coated sheet. However, the isocyanate used in the '426 system prevents the protective polymeric layer from being practically removed in a reasonable manner.
In view of the above, it can be seen that there exists a need in the art to better protect coated glass sheets in the processing stages prior to heat treatment (e.g., prior to tempering) in an efficient manner such that a protective layer(s) can be easily removed in a processing step prior to tempering. In particular, increased protection against mechanical abrasion and environmental damage is needed in steps leading up to heat treatment (e.g., thermal tempering).
In certain example embodiments of this invention, a temporary protective coating is provided on a glass substrate that is coated with a multi-layer low-E coating. The temporary protective coating includes one or more layers and is located on the glass substrate over at least the low-E coating.
In certain example embodiments, the temporary protective coating is designed such that it can be applied over a low-E coating in an efficient manner without the need for any sort of lengthy curing procedure. In this regard, the temporary protective coating is preferably applied in solid form (i.e., as opposed to liquid form) so that no significant curing is needed of the protective coating. Moreover, in certain example embodiments of this invention, the temporary protective coating is designed such that it can be easily removed by simply peeling it off just prior to heat treatment (e.g., just prior to tempering). In certain example embodiments, the temporary protective coating is designed such that it is not water soluble so that it remains on and protects the low-E coated glass substrate during washing step(s) and thereafter during at least some post-wash handling step(s).
In certain example embodiments of this invention, there is provided a method of making a window, the method comprising: forming a multi-layered low-E and/or solar control coating on a glass substrate; providing at least two flexible protective sheets in non-liquid form to the glass substrate over at least part of the low-E coating; applying at least one protective coating in liquid form, before and/or after the flexible protective sheets are provided, so as to reduce one or more gaps formed between the low-E coating and the flexible protective sheet(s) and/or between the flexible protective sheets; cutting, edge seaming, and/or washing the coated article with the protective coating and protective sheets thereon, and before or after the cutting, edge seaming and/or washing peeling the protective sheets and at least part of the protective coating off of the top surface of the low-E and/or solar control coating.
In other example embodiments of this invention, there is provided a method of making an insulating glass (IG) window unit, the method comprising: forming a multi-layered low-E coating on a glass substrate, wherein the low-E coating comprises at least one infrared (IR) reflecting layer comprising silver sandwiched between at least first and second dielectric layers; adhering at least two flexible protective sheets in non-liquid form to a top surface of the low-E coating via at least an adhesive layer to form a protected coated article; applying at least one protective coating in liquid form directly on the low-E coating and/or over at least one of the flexible protective sheets in order to reduce one or more gaps formed between the low-E coating and the flexible protective sheet(s) and/or between the flexible protective sheets; following applying and curing of the protective coating, shipping the protected coated article to a fabricator of IG window units; the fabricator cutting the protected coated article into an appropriate shape and size with the protective sheets thereon, edge seaming the protected coated article with the protective sheets thereon, and/or washing the protected coated article with the protective sheets thereon, so that following the cutting, edge seaming, and/or washing the protective sheets and protective coating remain at least partially adhered to the top surface of the low-E coating; following said cutting, edge seaming, and/or washing, peeling the protective sheets off of the top surface of the low-E coating to form an unprotected coated article, and also removing at least part of the protective coating when peeling off the protective sheets; after peeling the protective sheets off of the top surface of the low-E coating, thermally tempering the coated article including the glass substrate and low-E coating; and after said tempering, coupling the tempered coated article including the glass substrate and low-E coating to another glass substrate to form an IG window unit.